Blank and method for making commutators



April 1936- F. w. COTTERMAN v 2,038,419

BLANK AND METHOD FOR MAKING COMMUTATORS Filed Jan. '7, 1935 INVENTOR WWW A TTORNE Y Patented Apr. 21, 1936 UNITED STATES PATENT OFFIC BLANK AND IVIETHOD FOR MAKm'G COMMUTATORS Application January 7, 1935, Serial No. 673

14 Claims. (Cl. 29-15554) This invention relates to commutators, and particularly to commutators of the type wherein a plurality of segments of conductive material are imbedded in and circumferentially spaced apart around a core of molded insulation.

An object of the invention is to provide a commutator ring for such a commutator wherein the entire number of segments may be maintained in one piece until after the core is molded into them, then readily divided into separate segments with a minimum expenditure of labor, and with minimum waste of material, all without weaken ing the core.

Another object is to provide an unique procedure for making such a ring.

Another object is to so construct the ring as to make itequally adaptable to either an undercut commutator or a flush type commutator.

- Another object is to provide a method of making a complete commutator from such a ring.

I attain these and other objects by the procedure and in the resulting product hereinafter described, reference being had to the drawing wherein-- a Fig. 1 is a plan view of a strip of sheet metal partly fabricated in its process of being made into a series of interconnected commutator segments.

Fig. 2 is an end view of the strip shown in Fig. 1.

Fig. 3 is an edge view of a complete set of the commutator segments as they appear prior to being bent in the form of a commutator cylinder, the'said segments being interconnected by a series of integral end bridges.

Fig. 4 is an end view of the strip shown in Fig. 3.

Fig. 5 is a bottom view of the strip shown in Fig. 3.

Fig. 6 shows the strip Figs. 3, 4 and 5 bent to form the commutator cylinder.

Fig. 7 is a transverse section thru a mold body into which the cylinder Fig. 6 is placed.

Fig. 8'shows ,the commutator cylinder Fig. 6 in a mold after a core of insulation has been molded into it.

Fig. 9 is a transverse section taken at 99 of Fig. 8.

Fig. 10shows the complete commutator resulting from cutting off the ends of the core and with them the bridges connecting the segments.

Similar numerals refer to several parts throughout the several views.

In carrying out my process I may provide a roll of ribbon stock, preferably copper, of uniform width as at In and pass it continuously 5 thru a punch press provided with a progressive die. The entire roll is preferably passed thru the progressive die whereby uniformly spaced notches l l are cut in the edges of the strip leaving oppositely extending anchors l2. Rectangular slots l3 are punched thru the strip. at intervals equal 5 to the spacing of the notches I I. This procedure provides a. series of commutator segment blanks l4 each having oppositely extending anchors I2, adjacent segment blanks being connected at the ends by the integral bridges l6. 1|) Furthersteps in the progress of the strip thru the die comprise curling under the anchors l2 as at I! and bending the bridges l6 downwardly as at I 8. The bending of the bridges narrows the rectangular slots l3 to about one-third their 15 original width as at H! thereby bringing adjacent segment blanks I4 closer together. An entire roll of the strip may be thus punched into a plurality of spaced apart end connected commutator segments. 20

The strip of interconnected segments is next cut into cylinder-blanks 2| wherein each cylinder-blank contains the proper number of segments desired for the commutator.

The edge, end and bottom views Figs. 3, 4 and 5 25 respectively show the set of segments, each curved on the outside as at 22 to correspond to the radius of the commutator cylinder, each segment having on its ends the downwardly curled anchors I1,

and the adjacent segments being connected by 30' the bent bridges l8.

A blank 2| is next bent into the form of 2. cylinder as at 23 Fig. 6, both the anchors I! and the segment connecting bridges l8 extending radially inward toward the axis of the commutator 35 cylinder. It will be seen that, because of the manner in which the bridges l8 are formed, the slots l9 which separate the several segments of the ring 23 extend thruout the length of the ring, so that it may readily be passed axially into a 40 cylindrical mold body 24, Fig. 7, which has the inwardly extending spacing tangs 26.

In Figs. 8 and 9 the complete mold 21 is shown with a core. 28 of insulation molded into the commutator ring 23. The mold comprises the 45 body 24 having the inwardly extending spacing tangs 26, a center plug 29 and a plunger 3|. The center plug 29 and the lower end of the plunger 3| are formed as at 32 and 33 respectively whereby the ends of the core 28 are depressed, leaving 50 at each of said ends an annulus 34 within which the bridges l8 are contained. It will be observed that the anchors I! are so imbedded in the core 28 that the annuli 34 may be cut oil without disturbing the anchors, and that when the annuli are so cut oi! the bridges II will be cut oil with them, whereby the theretoi'ore one piece com; mutator-ring becomes a series oi electrically and mechanically separated segments i4 imbedded in the insulating core 28.

Fig. 10 shows the completed commutator struc ture I! after the annuli 34 containing the bridges II have been removed. The core 28 has acentral shaft opening 31, left where the center plug 28 was withdrawn, and the segments it are securely held to the core by the anchors i1, each segment being separated from the next by the spaces I! from which the spacers 26 01 the mold body 24 were withdrawn.

The commutator II belongs to the class which is usually termed undercut, that is, commutators wherein the insulation composing. the core does not extend outwardly between the segments to the brush track. In molded commutators having cores containing a high percentage oi resin, undercutting is highly essential ii a reasonably high voltage is to be permitted, for otherwise the arcing oi the brushes converts the resin to carbon and shorting between the segments results. But it will of course be understood that, where voltage and speed conditions permit it, a flush type commutator, that is, one wherein the material comprising the insulation core may extend also outwardly between the segments to the brush track, my be desirable. Such a flush type commutator may be readily produced by my process merely by removing the spacers 28 from the mold body 2|, all other steps of the procedure remaining substantially the same.

From the foregoing disclosure it will be apparent that a number of advantages are had by making commutators according to my invention. First, the wide slot l8, Fig. l, is more easily punched than a narrow slot I! would be and the punches are less easily broken. Therefore by punching the slot wide as at ll, then narrowing it as at ID, less costly dies and less broken punches will result.

Second, forming the segment connecting bridges downwardly, as at ll, Fig. 3, not only takes up the surplus length of the bridges, so as to narrow a slot II to compose a slot it, but it provides clearance slots I9, Fig. 6, thru whichthe spacers 28, Fig. '1, necessary in making an undercut commutatonlmay slide axially when the cylinder 23 is inserted and removed from the mold.

Third, by providing from a one piece sheet metal stamping, a commutator cylinder 23, Fig. 6, wherein the segment-connecting bridges ii! are axially beyond the inturned anchors H, the bridges may be removed without cutting into the anchors, with little expenditure of labor and with simple tools.

Believing the procedure and product hereinbeiore disclosed to constitute a considerable advancement in the commutator art,

I claim- 1. A commutator cylinder comprising a series of circumferentially spaced apart commutator segments each having an integral portion at each of its ends turned radially inward then axially toward each other to compose anchors, the ends of the several segments being connected at both ends by integral portions comprising bridges located axially beyond the said anchors.

2. A commutator cylinder comprising a series of circumierentially spaced apart commutator segments, the said segments being connected to each other at both of their ends by a series 0! integral bridges each extending radially from the, end of a segment toward the axis, then circumierentially, then radially away from the axis to the adjoining segment.

3. The structure defined in claim 2 wherein each segment has'two anchor portions one at each end extending from the segment toward the axis, the said bridges being situated axially beyond the said anchors.

4. The structure defined in claim 2 wherein each segment has an integral part 0! both of its ends turned radially inward tocompose a pair 01' anchors, the bridges being located axially beyond the said anchors.

5. Steps in the. method of making a commutator cylinder blank comprising a series of interconnected commutator segments, which consist of punching the series of segments from sheet metal with relatively wide parallel spaces between adjacent segments, and with bridges at both ends of the said segments extending from each one of said segments across one of said wide spaces to the next said segment, and bending said bridges to take up their length to thereby make said wide parallel spaces narrower.

6. Steps in the method 01' making a commutator cylinder comprising a series of interconnected commutator segments which consist of taking the steps defined in claim 5, then bending the blank in the form or a cylinder so that the downwardly bent bridges extend radially inward toward the axis of the cylinder.

7. Steps in the method of making a commutator cylinder comprising a series or interconnected commutator segments, which consist of punching from sheet metal a series 01' segments with open spaces therebetween, said segments having integral bridges connecting adjacent segments at the ends of said open spaces and integral anchors extending from the ends or the segments, bending the anchors downwardly to cause a pair of anchors at opposite ends or a segment to be closer together than a pair of bridges at opposite ends of one or said open spaces, then bending said commutator segments into the form of a cylinder with the downwardly bent anchors extending radially inward toward the cylinder axis.

8. Steps in the method 01' making a commutator, which consist ot-providing the commutator cylinder defined in claim 1, molding a core of insulation into the cylinder and about the anchors and bridges, hardening said insulation. then cutting oi! both ends of the core in planes transverse to the axis and between said anchor and said bridges.

9. Steps in the method of making a commutator, which consist of providing the commutator cylinder defined in claim 2, placing it in a mold having means which will fill the spaces between the segments and between the radially extending portions of the bridges, molding a core of insulation into the cylinder, hardening said insulation, then cutting thru the core in two planes both transverse to the axis and both immediately inside the said bridges.

10. A method of making a commutator which comprises cutting from a strip oi sheet metal a series of commutator segments, each segment having a pair of integral anchors extending oppositely from the ends and adjacent segments being connected by integral bridges at the ends of the said wide spaces, a pair of said anchors being closer together than a pair of said bridges, bending the pairs oi. anchors and the pairs (1 bridges downwardly whereby the spaces between the segments are decreased in width, bending the strip to cylindrical form with the anchors and bridges extending radially inward toward the axis of the cylinder, molding a core of insulation into the cylinder and about the anchors and bridges, hardening said insulation, then cutting ofi the ends of the core containing said bridges.

11. A commutator cylinder comprising a series of segments, inturned anchors at the ends of the segments, and integral bridges connecting said segments, said bridges extending from each segment first axially away from the segment, then radially inward, then circumferentially, then radially outward, then axially toward and to the adjacent segment.

12. The structure defined in claim 11 wherein there are anchors and bridges at both ends of each segment. 1

axially toward and to the next segment,

14. In a punched sheet metal blank for a com mutator cylinder, connnutator segments separated from each other by parallel spaces, the segments having anchors extending laterally away from the ends, and integral bridges extending first laterally away from the ends, then across at v the ends of the parallel spaces then laterally back to the next segment.

FREDERICK W. CO'I'IERMAN. 

